JP2002-118981A published by the Japan Patent Office in 2002 discloses a power source device for a vehicle using a fuel cell power plant and a secondary battery. The vehicle is driven using an electric synchronous motor controlled via an inverter.
The fuel cell power plant and a DC/DC converter which converts the voltage of the secondary battery are connected in parallel to the inverter. The inverter varies the direct current supplied from the fuel cell power plant or the DC/DC converter to a three-phase alternating current having an arbitrary frequency. The resulting current drives the electric synchronous motor used for driving the vehicle.